In many cases, a torque converter is provided with a lock-up device for directly transmitting torque from a front cover to a turbine. As described in Japan Laid-open Patent Application Publication No. JP-A-2010-031951 and so forth, the lock-up device includes: a piston that can be frictionally coupled to the front cover; a drive plate fixed to the piston; a plurality of torsion springs supported by the drive plate; and an output plate elastically coupled to the piston through the plural torsion springs in a rotational direction. The output plate is fixed to the turbine.
The piston axially divides the space between the front cover and the turbine, and is axially movable by difference in hydraulic pressure between the axially divided spaces. Further, when a lock-up clutch is turned on (power is transmitted), the hydraulic pressure is controlled such that the hydraulic pressure on the turbine side of the piston can be greater than that on the front-cover side of the piston. Accordingly, the piston is moved towards the front cover, and a friction facing mounted to the outer peripheral part of the piston is pressed onto the friction surface of the front cover. Therefore, the torque from the engine is directly transmitted from the front cover to a turbine-side member.